In the study, researchers asked 66 women "with significant fear of spiders," and assigned them to one of four groups, Sleep, Wake, Morning and Evening. The participants completed exposure therapy sessions (where they watched YouTube videos of spiders) at different times of day, and were later measured for their fear and anxiety levels. Those who watched the videos at night, and had 12 hours of sleep, responded better the next day to the therapy. On the other hand, those who were exposed to spiders in the morning reported higher levels of anxiety when tested later in the day. The researchers looked at skin conductance response (SCR), which they measured with sensors to determine the participants' physical reaction to the spiders.

According to the researchers: "In order for exposure therapy to be successful, consolidation and retention of extinction learning acquired during therapy is essential. ... Sleep enhances consolidation of emotional memory. ... Following a 12-hour delay, those exposed in the evening, who then slept, showed better extinction retention and generalization when tested in the morning than those exposed in the morning who remained awake until tested in the evening."